The Eagles have starting cornerbacks Cary Williams and Bradley Fletcher switch sides during practice. They do this in case defensive coordinator Bill Davis wants to have one of them follow an opposing wide receiver around the field during a game.

That has not been Davis' preferred style this season. He has kept the starting cornerbacks on designated sides - Williams on the right, Fletcher on the left - and that's expected to continue when the Eagles face the Dallas Cowboys on Sunday.

It means that Williams and Fletcher will get turns against Cowboys receiver Dez Bryant, one of the NFL's top pass catchers. They also will have to defend against Terrance Williams, an impressive rookie, and Miles Austin, a former Pro Bowler. Those receivers will catch passes from quarterback Tony Romo, who has completed 70.2 percent of his passes and has 14 touchdowns and just three interceptions this season.

"There's a comfort zone that the corners get in on their sides and who they are working with," Davis said. "Now, I break that comfort zone every day in practice, so they switch every day so I can do it if I want. But right now there really hasn't been a situation to say, 'Hey, this will benefit us more than just keeping them in their comfort zone.' "

Williams and Fletcher were signed during the offseason to be the starting cornerback duo, replacing Nnamdi Asomugha and Dominique Rodgers-Cromartie. The free-agent class was crowded with starting cornerbacks. What stood out to the Eagles was the size of the two and their physical play.

Williams related how he would play against Bryant without any hesitation: "As far as I'm concerned, I'm going to get up in his face."

Teams have tried different ways to cover Bryant, who has 34 catches for 459 yards and six touchdowns. Cowboys coach Jason Garrett said defenses have shown a variety of coverages, from having one cornerback chase Bryant around the field to rolling help to Bryant's side or putting two defenders over the top.

"I understand giving him a free run isn't necessarily the best thing," Williams said. "We're going to throw a lot of things at the guy. You don't want him to get too settled and be able to run free and make moves whenever he gets the ball in his hands."

Garrett called the Eagles' starting cornerbacks "athletic" and "long" - attributes that coach Chip Kelly seeks at the position. The Cowboys receivers are big and physical, so Sunday makes for a compatible matchup.

Fletcher said the Eagles cornerbacks must study all of the Cowboys receivers because the Eagles play the sides and not the man. That means the cornerback sometimes must adjust the style depending on the receiver, although Williams said he continues to press because that's what he does best.

"Some guys are better against the press, some guys you can read easier if you're playing off," Fletcher said. "It's a little of everything. It's something we need to figure out as corners: What's the best thing I can do against this guy?"

Kelly said that when the Eagles signed Fletcher and Williams, he was thinking about defending against the rangy receivers in the NFC East. The coach said it's clear that the Cowboys move Bryant around, giving the defenses different looks and matching him up against different defenders. The Eagles have played against top receivers Pierre Garcon, Demaryius Thomas, Vincent Jackson, Hakeem Nicks, and Victor Cruz, but this will be the toughest matchup yet.

"We've got to be great with our one-on-one matchup of both corners," Kelly said. "Fletch and Cary have to be great in their individual coverage on them because . . . you can't double a guy every play. So they will have plenty of times where they've got to just handle that and we will get help to them and zone over the top of them and use all of the different tools to help when you stop a star receiver."

Kelly pointed out that the risk in focusing too much on Bryant is that Terrance Williams, Austin, or tight end Jason Witten then beat you. Witten's 1,233 career receiving yards against the Eagles are the most he has had against any NFL team.

The Cowboys have played with an empty backfield more frequently this season, but Romo said they likely wouldn't do it as much against the Eagles because of the Eagles defense. However, with running back DeMarco Murray expected to miss the game with a sprained left knee, there could be even more emphasis on Dallas' passing game.

The burden will be on the Eagles cornerbacks more than anybody else. The Eagles need a pass rush, and the safeties must help over the top, but the defense cannot stop the Cowboys if Williams and Fletcher struggle.

"Those guys are really taking a step forward, and our press coverage is improving," Davis said. "It's moving forward with the techniques and the system. I think they are getting a comfort with the communication part of it, with the techniques I'm asking them to do within the calls."